Chapter 8

Mastering Whole Number Operations

Addition and Multiplication involves all single digit addends and factors

Addend plus addend equals sum Factor times factor equals product How many basic facts are there????

Basic Facts

100!!!! For each addition and multiplication

How???

Basic Facts

1. Understand the meaning of the operations 2. Use thinking Strategies to Retrieve Facts *use facts that they know to figure out facts that they don’t i.e. 2+2 =4 so 2+3 must be one more than that * other stategies include counting on, counting back, skip counting, one more, one less…

Three Step Approach to Fact Mastery

3. Using Consolidating Activities for Drill and Practice games , activities , worksheets all help children memorize these facts

Three step approach cont…

Counting on … 6+3 start from the 6 and count on three times seven, eight , nine

Remind children to start from the larger # regardless of order of the problem ..3+6 still starting at 6 and add on three more

This method works well for both addition and subtraction

Sometimes a calendar works as a good visual to use this method—see next slide

Thinking Strategies for Addition and Subtraction

January 2012Sunday Monday Tuesday Wednesday Thursday Friday Saturday

1 New Year’s Day

2 3 4 5 6 7

8 9 10 11 12 13 14

15 16 Martin Luther King Day

17 18 19 20 21

22 23 24 25 26 27 28

29 30  

31        

             

Use counters1. Show two groups of 62. “How much is 6+6?”3. Add one more to one of the groups4. Now we have 6 + 7. “How many

altogether?”5. One more than twelve6. Count out 13 objects with students7. 6+6 = 12 then 6 + 7 = 13

One more or one less

One addend is increased while the other addend is decreased by trying to make one addend 10

Use counters to model two piles 8 + 4=? Manipulate counters so one pile has 10 Now solve

Compensation

Order doesn’t matter 3+5 = 5+3

3•5 = 5•3However this does not work for Subtraction and Division6-4 ≠ 4-624/6 ≠6/24

Commutative Property of Addition and Multiplication

4 7 17 37 33 13 53 59 89

Calculator Game

John’s calculator is broken. The number 4 key will not work. How may possible combinations can you come up with on the screen to get 4 without actually using 4?

John has a math problem for hw and he is still trying to use the same calculator to solve this problem 24-4= ? Can you help him rewrite this problem so he can use his calculator?

Calculator/ broken calculator